I think we need a bit more information or some clarification here.
Your sims live in some other homeworld and perhaps by way of the NRaas Traveler mod they are visiting Union Cove? And the brother and the brother-in-law are supposed to be living back home but are each showing up twice in the relationship panel, both on the left side (not greyed out) and on the right side (greyed out)? If this is the case, sounds like copies of them got spawned as tourists. Usually Overwatch and ErrorTrap catch the duplicates and resolve them pretty soon if not right away when things like this happen, but that could also happen when they return back home. If I've described this correctly, do you have the latest versions of all NRaas mods?
Or have I misunderstood where you are, how your sims got there, and what you meant by "greyed out"?